In an MI5 report on the interrogation of Omar Deghayes, a Libyan-born British resident held by the Americans at Bagram airbase north of Kabul, an officer wrote to his superiors in London: "Deghayes was brought to the interview room manacled and hooded. When the hood was removed, Deghayes looked pale and shaky."

After offering water and asking Deghayes whether he felt well enough to continue, the officers introduced themselves as Paul and Martin, "and explained the role of MI5".

They warned Deghayes that he was facing a long period of incarceration in US hands and that they would not consider helping him unless he told them everything they wanted to know. Deghayes was mumbling and incoherent at times but the officers told him they knew he was lying when he answered questions about links with jihadist organisations in Libya.

After another interrogation a week later, an MI5 officer reported back to London that Deghayes was thinner but mentally alert. "Throughout the interview Deghayes expectorated rather disgustingly into a tissue as if he were still tubercular. These moments usually coincided with those answers where he was most evasive."

Deghayes told the officers that he was suffering internal bleeding and complained that no evidence had been presented against him. "He was also being treated badly, with head-braces and lock-down positions being the order of the day," wrote the officer. "He was treated better by the Pakistanis; what kind of world was it where the Americans were more barbaric than the Pakistanis? We listened but did not comment."

MI5 interrogated Deghayes again and told a senior American officer in Deghayes' presence, that the detainee had not been co-operating. "If he sticks to his story and just gives a few more details, we propose disengaging and allowing events here to take their course," the officer wrote.

In the autumn Deghayes was flown to Guantánamo Bay, where he stayed for more than five years. At one point he was so severely beaten that he was blinded in one eye.

These documents show Downing Street's interventions to deny consular services to detainees held in Guantánamo Bay and elsewhere. A telegram despatched by the foreign secretary, Jack Straw, to the embassy in Washington, shows that the government supported the transfer of British detainees to Guantanamo Bay